Numerical controller for wire electrical discharge machine

ABSTRACT

In wire electrical discharge machining, to make it possible to determine the state of rough machining or finishing in various stages, the machining speed, the working voltage, and execution portion information are stored as a set for each movement of a fixed distance in the process of execution of a plurality of times of machining in which rough machining through finish machining are consecutively executed, and are displayed in a two-dimensional graph.

TECHNICAL FIELD

The present invention relates to a numerical controller for displaying astate of machining of a wire electrical discharge machine.

BACKGROUND ART

In a wire electrical discharge machine, a wire electrode is disposed ata predetermined interval with respect to a workpiece, the workpiece andthe wire electrode are immersed in a processing tank, and a voltage isapplied between the workpiece and the wire electrode in this state.

The wire electrode and the workpiece are brought close to each other,and when the amount of the gap between the wire electrode and theworkpiece reaches a predetermined amount, electrical discharge takesplace between the wire electrode and the workpiece. As a result, theworkpiece is machined by this electrical discharge energy.

In such wire electrical discharge machining, it is necessary to maintainthe amount of the gap between the wire electrode and the workpiece to anoptimum amount so as to constantly maintain an optimum state ofelectrical discharge. However, as the workpiece is machined, the amountof the gap constantly changes, and debris is produced between theelectrodes, so that it is difficult to directly measure the amount ofthe gap.

On the other hand, in wire electrical discharge machining, asubstantially linear relationship holds between the amount of the gapbetween the wire electrode and the workpiece and a mean working voltageobtained by smoothing the working voltage, and to maintain the meanworking voltage to a fixed level is equivalent to holding the amount ofthe gap to a fixed amount. Accordingly, it becomes necessary to maintainthe mean working voltage to a fixed level by controlling the machiningspeed or the position of the wire electrode.

As described above, in wire electrical discharge machining, a closerelationship holds between the amount of the gap between the wireelectrode and the workpiece on the one hand, and the machining speed andthe working voltage on the other hand, and when analyzing the machiningand determining whether it is good or bad, it is extremely important touse tendencies and movements of the machining speed and the workingvoltage as materials for their judgement.

As a conventional technique of this type, one disclosed in JapanesePatent Unexamined Publication No. 264215/1991 has been known. FIG. 7 isa diagram explaining a conventional example. In the left-hand portion ofthe drawing, a machining configuration based on a machining program isdisplayed in advance (broken-line portion), and the present position(thick-line portion) corresponding to the position of the wire electrodeis displayed by being superposed thereon. In the right-hand portion ofthe drawing, the working voltage during machining and the time axis aregraphically displayed as being the ordinate and the abscissa,respectively. Further, there is a disclosure wherein a portion of themachining configuration is selected and displayed in enlarged form, andthe working voltage at the corresponding portion is displayed inenlarged form in interlocking relation to the enlarged display.

FIG. 8 is a diagram illustrating the relationship between the lapse ofthe machining time and the machining speed in the conventional example.However, in a case where machining is effected a plurality of timesranging from rough machining to finish machining with respect to thesame configuration, since the relationship between the machining speedand the voltage in the respective stages is overwritten, there is aproblem in that it is impossible to determine such as whether machiningin each stage is being effected appropriately, or at which stage ofmachining a problem exists.

DISCLOSURE OF THE INVENTION

The present invention has been devised to overcome the above-describeddrawbacks of the conventional art, and its object is to provide anumerical controller having a display means which compares and displaysin one two-dimensional graph items of machining-state detectioninformation on machining stages ranging from rough machining to aplurality of times of finish machining.

In a wire electrical discharge machine for producing electricaldischarge between a wire electrode and a workpiece and finishing theworkpiece a plurality of times from rough machining to finish machiningon the basis of a predetermined machining program, a numericalcontroller for a wire electrical discharge machine in accordance with afirst aspect of the present invention comprises:

machining controlling means for determining and controlling a machiningspeed of the wire electrode in accordance with a discharge gap betweenthe workpiece and the wire electrode or a state of electrical discharge;

machining-state detecting means for detecting machining-state detectioninformation such as a working voltage for each movement of apredetermined distance in a process of execution of machining based onthe machining program;

information-record storing means for correlating detection informationdetected by the machining-state detecting means, the machining speedgenerated by the machining controlling means, and machining positioninformation for each movement of the predetermined distance, and forstoring them in a storage device as machining-state detectioninformation records;

information-record reading means for reading the stored machining-statedetection information records from the storage device; and

two-dimensional graph displaying means for giving a graphic display byusing the machining-state detection information and the machining speed,which are the machining-state detection information records thus read,as elements of one of two axes of a two-dimensional graph and by usingthe machining position information of the machining program as anelement of the other axis thereof.

In a wire electrical discharge machine for producing electricaldischarge between a wire electrode and a workpiece and machining theworkpiece on the basis of a predetermined machining program, a numericalcontroller for a wire electrical discharge machine in accordance with asecond aspect of the present invention comprises:

machining controlling means for determining and controlling a machiningspeed in accordance with a discharge gap between the workpiece and thewire electrode or a state of electrical discharge;

machining-state detecting means for detecting machining-state detectioninformation such as a working voltage for each movement of apredetermined distance in a process of execution of machining based onthe machining program;

information-record storing means for correlating detection informationdetected by the machining-state detecting means, the machining speedgenerated by the machining controlling means, machining positioninformation for each movement of the predetermined distance, and atleast one of a sequence number, a block number, a machining start holenumber, and a number of finishing which are included in the machiningprogram, and for storing them in a storage device as machining-statedetection information records;

information-record reading means for reading the stored machining-statedetection information records from the storage device; and

display means for displaying a list of the machining-state detectioninformation records thus read.

A numerical controller for a wire electrical discharge machine inaccordance with a third aspect of the present invention, the machiningposition information is displayed by being correlated to blocks of themachining program.

Since the present invention is configured as described above, thepresent invention offers the following advantages.

In the numerical controller for a wire electrical discharge machine inaccordance with the first aspect of the present invention, themachining-state detection information, the machining speed generated bythe machining controlling means, and execution portion information ofthe machining program are formed as a set and are stored in the storagedevice as the machining-state detection information records, and thestored machining-state detection information records are read from thestorage device and are displayed in a two-dimensional graph.

Accordingly, it is possible to detect and determine whether roughmachining or finish machining in each stage is being effectedappropriately, or in which machining a problem lies in a midpointmachining stage due to changes in the machining speed, the workingvoltage, and the like.

In the numerical controller for a wire electrical discharge machine inaccordance with the second aspect of the present invention, themachining-state detection information, the machining speed, and theexecution portion information for correspondence with an executionportion, as well as the sequence number and the block number of themachining program, a cumulative distance of movement from a machiningstart point, a machining start hole number, and the number of finishing,are displayed in list form. Accordingly, it is possible to detect anddetermine whether rough machining or finish machining in each stage isbeing effected appropriately, or which position in the machining programis a problem in machining.

In the numerical controller for a wire electrical discharge machine inaccordance with the third aspect of the present invention, since adisplay is given by using as a reference the distance of movement apoint of origin in each block of the machining program, it is possibleto detect and determine whether rough machining or finish machining ineach stage is being effected appropriately, or at which position of theblock a problem has occurred.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram illustrating the configuration of the presentinvention;

FIG. 2 is a diagram illustrating values and an example of display ofmachining-state detection information records stored in a storagedevice;

FIG. 3 is a diagram in which a portion of a machining program displayedby way of a graphic simulation is range-designated by a rectangle;

FIG. 4 is a diagram illustrating the distribution of therange-designated information among the machining-state detectioninformation records;

FIG. 5 is a diagram in which machining information of different numbersof machining are graphically represented by being superposedtwo-dimensionally;

FIG. 6 is a diagram in which a display is given by connecting andcorrelating leading positions of the blocks without converting thedistances of movement on the axis of abscissas;

FIG. 7 is a diagram illustrating a display of a machining state in aconventional example; and

FIG. 8 is a diagram illustrating the relationship between a machiningpath and a machining speed in the conventional example.

BEST MODE FOR CARRYING OUT THE INVENTION First Embodiment

Referring to the drawings, a description will be given of an embodimentof the present invention. FIG. 1 is a diagram illustrating theconfiguration of a portion of a numerical controller for a wireelectrical discharge machine in accordance with the present invention.

Reference numeral 1 denotes a machining-state detecting means whichdetects the working voltage connected to a discharge circuit of the wireelectrical discharge machine, and the numerical controller is capable offetching the voltage during machining through this machining-statedetecting means. In this case, the working voltage serves asmachining-state detection information 2. It should be noted that it isalso possible to jointly display other parameters of such as the workingcurrent, working reaction force, working fluid temperature, and ambienttemperature as the machining-state detection information 2 other thanthe working voltage and fetch them into an information-record storagemeans 6 as machining-state detection information records 8.

Reference numeral 3 denotes a machining controlling means, which is abasic function of the numerical controller as is known. In the wireelectrical discharge machine, the machining controlling means 3 controlsthe relative movement of the wire electrode and the workpiece so as tomaintain the mean working voltage at a fixed level, as mentioned above.Machining speed data 4 generated by the machining controlling means 3 tomaintain the mean working voltage at a fixed level is imparted to adriving device 5 for effecting the relative movement of the wireelectrode and the workpiece. In addition, the machining speed data 4 isoutputted from the machining controlling means 3 to theinformation-record storage means 6 as machining result data, i.e., asthe machining-state detection information records 8.

The machining controlling means 3 further generates execution portioninformation 7 as well. As is known, machining based on the numericalcontroller is performed by consecutively interpreting and executing amachining program (NC program), and sequence numbers and block numbersare present for identifying blocks which are units of the machiningprogram. Since these can be recognized by the machining controllingmeans 3 in the execution of the machining program, they can be outputtedto the information-record storage means 6 as the machining-statedetection information records 8. In addition, the cumulative distance ofmovement from a machining starting point can also be generated by thenumerical controller by accumulating the moving distance data generatedin the execution of the machining program, and can be imparted to theinformation-record storage means 6.

To compare and display the relationship between the machining speed andthe voltage in the plurality of stages of machining ranging from roughmachining to finish machining with respect to the same configuration, itis possible to additionally use machining start hole numbers and thenumber of finishing as the execution portion information 7 therefor. Ina case where a plurality of machining start holes are provided in oneworkpiece, and machining of a plurality of configurations is effected,it becomes necessary to identify the machining portions, so that it isimportant to use the machining start hole numbers.

Although a method of instructing the machining start hole number is notset in the machining program, it is possible to use a variable of themachining program as a counter for counting the machining start hole, orallow the machining controlling means 3 to recognize the machining starthole number with an exclusive-use NC code allotted thereto.

As the machining-state detection information records 8, theinformation-record storage means 6 stores in a storage device 9 theworking voltage which is the machining-state detection information 2imparted from the machining-state detecting means 1, the machining speeddata 4 imparted from the machining controlling means 3, and the sequencenumber, block number, cumulative distance of movement, machining starthole number, and number of finishing which are the execution portioninformation 7.

An example of the structure of the machining-state detection informationrecords 8 is shown in FIG. 2. The working voltage which is themachining-state detection information 2, the machining speed data 4, andthe sequence number, block number, cumulative distance of movement,machining start hole number, and number of finishing which are theexecution portion information 7 are stored in the storage device 9 atpredetermined detection intervals.

The generation and storage of the aforementioned set of machining-statedetection information records 8 are executed for a predetermineddetection interval or each movement of a fixed distance in the processof execution of rough machining alone or in the process of execution ofa plurality of times of machining in which rough machining throughfinish machining are consecutively executed.

An information-record reading means 10 reads the machining-statedetection information records 8 from the storage device 9, and impartsthem to a two-dimensional graph display means 11.

Referring to FIGS. 3, 4 and 5, a description will be given below of themethod in which the graph display means 11 compares and displays therelationship between the machining speed and the working voltage in theplurality of machining stages ranging from rough machining to finishmachining with respect to the same configuration. It should be noted,however, that it is assumed that all the directions of machining pathsof the respective stages ranging from rough machining to finishmachining are identical.

Referring to FIG. 3, a description will be given of a step in which anoperator designates a range through a rectangle for range designation onthe screen so as to display the machining program used in machining bymeans of graphic simulation. In addition, FIG. 4 is a diagramillustrating the machining-state detection information records 8 storedin the storage device 9 by the information-record storage means 6.

Which rendering elements are included in the range-designated rectanglecan be detected from the machining program by a known graphicrepresentation technique. For example, whether or not rendering elementsare included in the range-designated rectangle are consecutivelydetermined in the process of rerendering the overall configuration.

If a determination is made that the rendering element is included, bymeans of an identification number allotted in advance to the renderingelement it is possible to specify a relevant portion of the machiningprogram, on which the generation of the relevant rendering element isbased. This identification number may be a record number (correspondingto a row number in FIG. 4) in a case where the execution portioninformation 7 (sequence number, block number, cumulative distance ofmovement, machining start hole number, and number of finishing)generated in the process of the graphic simulation of the machiningprogram is consecutively stored in a database.

Next, a description will be given of the step of extracting acorresponding portion in a plurality of times of machining.

To compare and display the relationship between the machining speed andthe working voltage in the plurality of machining stages ranging fromrough machining to finish machining, it is necessary to extractmachining-state detection records corresponding to each stage.Generally, since machining is effected by controlling the position ofthe wire electrode by changing the offset value of the machining programhaving the same path when the workpiece is subjected to rough machiningthrough finish machining, the respective distances of movement in themachining stages at an arcuate corner do not agree with each other.Accordingly, there are cases where only the cumulative distance ofmovement of the machining stages is insufficient to obtaincorrespondence with the machining stages.

On the other hand, the sequence number and the block number shouldbecome identical at each machining stage insofar as the same machiningprogram is used by being invoked. Accordingly, it is possible to adopt amethod in which a corresponding block is fist specified by the sequencenumber and the block number, and correspondence is then obtained by thecumulative distance of movement for each corresponding block.

A description will be given of the step of extracting a correspondingblock.

Here, to simplify the description, it is assumed that rendering elementscorresponding to a plurality of machining start holes are not includedin the range-designated rectangle. Namely, it is assumed that thedesignation of the range is effected with respect to only oneconfiguration as shown in the broken-line frame in the left half portionof FIG. 3.

Among the rendering elements which are included in the rectangle when arange is designated, a plurality of execution portion informationrecords ranging from rough machining to finish machining are specifiedin mixed form. Here, a description will be given of a case where anexecution portion information record in rough machining is used as areference, and an execution portion of finish machining correspondingthereto is extracted.

As shown in the broken-line frame in the left half portion in FIG. 3, afirst record which is rough machining (this is the case where thenumber-of-finishing data is 1, and is also called 1st cut) is searchedfor among the execution portion information records specified in therange designation. This is set as a record A(1). Incidentally, thenumeral in the parentheses, which is an index of A, represents thenumber of machining. Next, among all the records, an initial recordwhich is rough machining and has the same values as those of thesequence number and the block number of the record A(1) is searched for.This is set as a record B1(1). Subsequent records are represented asBm(n) in which the numeral following B represents the block number (mth)in the designated range, and the subsequent numeral in the parenthesesrepresents the number of machining (nth) ranging from rough machining tofinish machining. Namely, the record B1(1) is the execution portioninformation record at the portion where the block of the machiningprogram at the rough machining portion included in the range-designatedrectangle starts. There are cases where B1(1) is not included in therange-designated rectangle as in the case of the solid-line frame in theright half portion in FIG. 3.

Further, if different blocks are included in the range-designatedrectangle, such blocks are consecutively determined as records B2(1) andB3(1). Next, among all the records, an initial record whosenumber-of-machining data is 2 (called 2nd cut) and which has the samesequence number and block number as the record B1(1) is searched for.This is set as a record B1(2), and the subsequent records are set asrecords B2(2) and B2(3).

Thereafter, records Bm(3) and Bm(4) corresponding to the numbers offinishing 3 and 4 are searched for in a similar manner, and extractionends when the search becomes impossible.

Next, a description will be given of the step of determining theabscissa.

As described above, the distances of movement in the blocks representedby the records Bm(n) do not necessarily agree with each other.Accordingly, an actual distance of movement from a leading position ineach block is converted.

If it is assumed that the distance of movement LENG in the block isLENGm(1) in the case of rough machining and LENGm(n) in the case offinish machining, that the actual distance of movement from the leadingposition is Posm(n), and that the value used for the abscissa isPosYm(n), the abscissa distance PosY on the display means 11 iscalculated as PosYm(n)=Posm(n)·(LENGm(1)/LENGm(n)).

As described above, as the actual distance of movement Posm(n) from theleading position is converted to the value PosYm(n) used for theabscissa, even if the actual distances of movement differ due to theoffset value, it becomes possible to cause the respective distances ofmovement in the respective machining stages to substantially agree witheach other.

A description will be given of the step of rendering abscissa data.

The data in FIG. 4 is read by taking as the abscissa the data convertedin the above-described step of determining the abscissa and by taking asthe ordinate the corresponding working voltage and the machining speed,and a two-dimensional graphic display is given as shown in FIG. 5. Atthis time, as information on the machining of different numbers ofmachining is displayed in a superposed manner on the same graph, itbecomes possible to read the correlation between the machining stages,and it becomes possible to determine the number of machining whichexerted a large influence or the number of machining up to whichmachining was satisfactory.

In giving the above-described display, as the method of effecting rangedesignation for two-dimensional display, it is assumed that what isincluded in the rectangle is selected, but a starting point and aterminating point may be selected by directly pointing them on thesimulation screen, or machining-state detection information data may bedirectly selected.

In addition, the directions in which machining paths of rough machiningand finish machining are traced are assumed to be identical in allmachining; however, in wire electrical discharge machining, there arecases where after rough machining is completed, the machining path offinish machining is traced in the opposite direction. In such a case,machining information of odd occasions is read in the forward direction.However, since it is possible to read machining information of evenoccasions in the backward direction, a plot can be made in the identicaldirection, and machining information at the same positions can bedisplayed on the two-dimensional graph while maintaining registry of themachining positions by the block numbers in the machining information.Therefore, the directions in which the machining paths are traced maynot be identical.

In addition, although the distance of movement LENGm(1) of roughmachining is used as the reference as the value used in the display ofthe abscissa, even if the distance of movement LENGm(n) of finishmachining is used, the width of the overall graph only changes, and thecorrelation does not change. Further, if it is assumed that a virtualdistance of movement without an offset is LENGm(0), an actual distanceof movement PosY may be calculated and displayed by using this LENGm(0)as the reference.

In addition, the state of machining of a machined portion can beestimated by displaying the value of the distance of movement used inthe abscissa as an actual distance of movement irrespective of theoffset value and by connecting the leading ends of the blocks by a line.

INDUSTRIAL APPLICABILITY

As described above, the wire electrical discharge machine in accordancewith the present invention is capable of detecting changes of the stateof machining from rough machining to finish machining by correlating thechanges to the positions in the machining program, so that the wireelectrical discharge machine in accordance with the present inventionfacilitates improvement of the state of machining and can be used inhighly efficient wire electrical discharge machining operations.

What is claimed is:
 1. A numerical controller for a wire electricaldischarge machine producing electrical discharge between a wireelectrode and a workpiece and finishing the workpiece a plurality oftimes from rough machining to finish machining on the basis of apredetermined machining program, said numerical controller comprising:machining controlling means for determining and controlling a machiningspeed of the wire electrode in accordance with a discharge gap betweenthe workpiece and the wire electrode or a state of electrical discharge;machining-state detecting means for detecting machining-state detectioninformation including a working voltage for each movement of apredetermined distance in a process of execution of machining based onthe machining program; information-record storing means for correlatingthe machining-state detection information detected by saidmachining-state detecting means, the machining speed generated by saidmachining controlling means, and machining position information for eachmovement of the predetermined distance, and for storing them in astorage device as machining-state detection information records;information-record reading means for reading the stored machining-statedetection information records from said storage device; andtwo-dimensional graph displaying means for giving a graphic display byusing the machining-state detection information and the machining speed,which are the machining-state detection information records thus read,as elements of one of two axes of a two-dimensional graph and by usingthe machining position information of the machining program as anelement of the other axis thereof.
 2. The numerical controller for awire electrical discharge machine according to claim 1, wherein themachining position information is displayed by being correlated toblocks of the machining program.
 3. A numerical controller for a wireelectrical discharge machine producing electrical discharge between awire electrode and a workpiece and machining the workpiece on the basisof a predetermined machining program, said numerical controllercomprising: machining controlling means for determining and controllinga machining speed in accordance with a discharge gap between theworkpiece and the wire electrode or a state of electrical discharge;machining-state detecting means for detecting machining-state detectioninformation including a working voltage for each movement of apredetermined distance in a process of execution of machining based onthe machining program; information-record storing means for correlatingdetection information detected by said machining-state detecting means,the machining speed generated by said machining controlling means,machining position information for each movement of the predetermineddistance, and at least one of a sequence number, a block number, amachining start hole number, and a number of finishing which areincluded in the machining program, and for storing them in a storagedevice as machining-state detection information records;information-record reading means for reading the stored machining-statedetection information records from said storage device; andtwo-dimensional graph displaying means for giving a graphic display byusing the machining-state detection information and the machining speed,which are the machining-state detection information records thus read,as elements of one of two axes of a two-dimensional graph and by usingthe machining position information of the machining program as anelement of the other axis thereof.
 4. The numerical controller for awire electrical discharge machine according to claim 3, wherein themachining position information is displayed by being correlated toblocks of the machining program.